How often are you updating the json values? 10/s? 100/s? 1M/s?
How many string keys? Millions? Billions? What happens if you lose an update?
Redis great for lots of rapid reads and moderate write speed for data that fits on a single server or can be manually sharded well (if it's straight k=>v, as you describe, that basically means your json fits in RAM; if you're using larger objects like sets/zsets/etc, it becomes a slightly different discussion), as long as your application can lose a few seconds without killing you (BGSAVE isn't instantaneous, of course).
How many string keys? Millions? Billions? What happens if you lose an update?
Redis great for lots of rapid reads and moderate write speed for data that fits on a single server or can be manually sharded well (if it's straight k=>v, as you describe, that basically means your json fits in RAM; if you're using larger objects like sets/zsets/etc, it becomes a slightly different discussion), as long as your application can lose a few seconds without killing you (BGSAVE isn't instantaneous, of course).